1. Field of the Invention
The present invention relates to a method of and an apparatus for processing image data to reproduce a halftone image, and more particularly to a method and an apparatus in which said image processing is effected on digitized image data.
2. Description of the Related Art
Image processing based on digital image signals tends to produce a distorted output signal due to a quantizing error even when the input signal varies smoothly. Distortions of the output signal appear as a pseudo contour (tone jumps) on the reproduced image, resulting in a reduction in the image quality. Particularly, in an image processing system which repeats image processing in a multi-stage configuration, repeated information drops tend to occur due to the limited accuracy in arithmetic operations. In such a system, any reduction in the image quality due to a quantizing error is the most serious problem.
The quantizing error may be lowered by reducing the duration of each quantizing step. However, such a solution requires an expensive analog-to-digital converter that is used to convert an input signal to a digital signal, or a large-scale image processing system.